Biofertilizer: Usage, Potential and Prospects as Alternative To

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They play a vital role in maintaining a long term soil fertility and sustainability. .... Establishment of "Bio-fertilizer Act" and strict regulation for quality control in ...
Biofertilizer: Usage, Potential and Prospects as Alternative To Chemical Fertilizer in Nigeria.

*Salihu Shina [email protected] *National Cereals Research Institute, Moor Plantation, Ibadan, Nigeria.

ABSTRACTS Farmers in Nigeria use more chemical fertilizers than the recommended levels for many crops. Excessive use of chemical nitrogen fertilizer not only accelerates soil acidification but also risks contaminating groundwater and the atmosphere and to achieve food security through sustainable agriculture, the requirement for fixed nitrogen must be increasingly met by BNF rather than by industrial nitrogen fixation. Biofertilizer are cost effective, eco-friendly and renewable source of land nutrient. They play a vital role in maintaining a long term soil fertility and sustainability. Biofertilisers enhance the nutrient availability to crop plants (by processes like fixing atmosphere N or dissolving P present in the soil); and also impart better health to plants and soil thereby enhancing crop yields in a moderate way. It is a natural method without any problems like salinity and alkalinity; soil erosion etc. this paper tries to review the potentials and prospects of biofertilizer usage in the country, the challenges that are encountering in the process and the overall gains for both farmers and the government. Keywords: Nigeria, biofertilizer, chemical fertilizer, soil fertility and BNF.

INTRODUCTION With the introduction of green revolution technologies, modern agriculture is getting more and more dependent upon the steady supply of synthetics inputs (mainly fertilizers).However adverse effects are been noticed due to the excessive and imbalanced use of these synthetics inputs. The illeffects being displayed gradually include leaching out, polluting water basin which results in high fish mortality rates and severely reducing the water quality, destroying microorganism and friendly insects, making crop more susceptible to the attack of diseases.The aforementioned effects of chemical fertilizers have brought about the need for alternatives such as biofertilizers; Biofertilizers is defined as a large population of specific or group of beneficial microorganisms for enhancing the productivity of the soil either by fixing atmospheric nitrogen or by solubilizing soil phosphorus or by stimulating plant growth through the synthesis of growth promoting substances Rajan (2002).Biofertilizers help to correct the ill-effects of chemical fertilizers since they do not contain traces of hazardous and poisonous materials. Also they are cost effective, eco-friendly (as it will not pollute the environment) and convenient to use safely. The advantage of biofertilizers over chemical fertilizers is enormous; they provides certain growth anti-fungal promoting substances like hormones, vitamins, amino acid 1

e.t.c while crops have to be provided with chemical fertilizers repeatedly to replenish the loss of nutrient utilized for crop growth, biofertilizers supply the nutrients continuously throughout the entire period of crop growth in the field under favourable conditions. The continuous use of chemical fertilizer adversely affects the soil structure whereas biofertilizers when applied to soil improve the soil structure and quality of crop products, increase in crop yield by 20 - 30%, replacement of chemical nitrogen and phosphorus by 25%, also chemical fertilizers are toxic at higher dose while biofertilizers have no toxic effects (Gyaneshwar et al., 2002).The soil microorganisms used in production of biofertilizers are phosphate solubilizing bacteria like B. magaterium, Pseudomonas striata, the nitrogen fixers like Azospirillum, Azotobacter, BGA, and Rhizobium, and phosphate mobilizing Mycorrhiza have been widely accepted as bio-fertilizers. (Rodriguenz et al., 1999). Need For Biofertilizers. Indiscriminate use of synthetic fertilizers has led to the pollution and contamination of the soil, polluting water basins, destroying micro-organisms and friendly insects, making the crop more prone to diseases and reduced soil fertility. And the high cost of chemical fertilizers which is becoming unaffordable by small and marginal farmers, and the huge amount of foreign exchange invested in the importation of synthetic fertilizers can be drastically reduced by using the biofertilizers instead. Besides above facts, the long term use of bio-fertilizers is economical, eco-friendly, more efficient, productive and accessible to marginal and small farmers over chemical fertilizers (FEPSAN, 2011) .Also an earlier work carried out by Chima et al (2013) on organic waste and biogas production, they conclude that Nigeria will be able to generate about 88.19 million tons of dry biofertilizer from biogas technology per annum. This is about 13 times the tonnage of synthetic fertilizer consumed in Nigeria between 2001 and 2010, for which the Federal Government of Nigeria spent N 64.5 billion ($ 410, 828, 025.48) on fertilizer subsidy. This potential amount of dry biofertilizer obtainable is valued at N 3.53 trillion ($ 22.77 billion) per annum. The Roles of Biofertilizers in Crop Production Soil microorganisms play significant roles in regulating the dynamics of organic matter decomposition and the availability of plant nutrients such as N, P and S (Silva et al., 2001). It is well recognized that microbial Inoculants constitute an important component of integrated nutrient management that leads to sustainable agriculture. In addition, microbial inoculants can be used as an economic input to increase crop productivity. A healthy plant usually has a healthy rhizosphere which would be dominated by beneficial microbes. Conversely, in unhealthy soil, dominated by pathogenic microbes, optimum plant growth would not be possible (Young et al., 2003). The following are microorganisms used as biofertilizers and their functions. a. Rhizobia: Rhizobia are symbiotic bacteria that fix atmospheric N2 gas in plant root nodules and have a mutually helpful relationship with their host plants. The plant roots supply essential minerals and newly synthesized substances to the bacteria. It is reported that Rhizobium can fix 50 – 300kg N/ha. (Ratti et al., 2002). b. Azotobacters and Azospirillum: These are free living bacteria that fix atmospheric nitrogen in cereal crops without any symbiosis and they do not need a specific host plant. Azotobacters are abundant in well drained, neutral soil, produce anti-fungal compounds, increase germination and vigor in young plants. They can fix 15 – 20kg/ha N per year (Kundu et al., 2002). c. Phosphate Solubilizing Bacteria (PSB): Under acidic or calcareous soil conditions, large amount of phosphorus are fixed in the soil but are unavailable to the plants. Phosphobacterins, mainly bacteria and fungi, can make insoluble phosphorus available to the plant. The solubilization effects of phosphobacterins is generally due to the production of organic acids that lower the soil pH and 2

bring about dissolution bound of forms of phosphate. It is reported that PSB culture increased yield of cereals up to 200 – 500 kg/ha and thus 30 –50kg of superphosphates can be saved (Kunda et al., 2005). d. Vesicular Arbuscular Mycorrhiza (VAM) Mycorrhizae are mutually beneficial (symbiotic) relationships between fungi and plant roots; VAM fungi infect and spread inside the root. Fungi aid in transmitting nutrients and water to the plant roots. They increase seedling tolerance to drought and high temperatures. e. Plant Growth Promoting Rhizobacteria (PGPR) PGPR represent a wide variety of soil bacteria which when grown in association with a host plant, result in stimulation of host growth. PGPR help in fixing N2 and increasing the availability of nutrients in the rhizosphere. They influence root growth and morphology and promote other beneficial plant – microbe symbioses (Ratti et al., 2001). f.

Blue Green Algae (Cyanobacteria) and Azolla: These belongs to eight different families, phototrophic in nature and produce Auxin, Indole acetic acid and Gibberllic acid, fix 20-30 kg N/ha in submerged rice fields as they are abundant in paddy, so also referred as ”paddy organisms”. N is the key input required in large quantities for low land rice production. Soil N and BNF by associated organisms are major sources of N for low land rice. (Wani et al., 1995)

Inoculation of Biofertilizers Application of the microbial biofertilizer is an important step in the Biofertilizer technology. If the microbial inoculants are not applied properly, the benefits from the biofertilizer may not be obtained. During application one should always remember that the most of the microbial biofertilizers are heterotropic, i.e. they cannot prepare their won food and depend upon the organic Carbon of soil for their energy requirement and growth. So, they either colonize in rhizosphere zone or live symbiotically within the root of higher plants. The bacteria which colonized the rhizosphere zone obtain their organic carbon compounds from the root exudes of the higher plants. The symbiotic ones obtain organic carbon directly from the root. So, microbial inoculants must be applied in such a way that the bacteria will be adhered with the root surface. Biofertilizers are generally applied to soil, seeds or seedling, with or without some carrier for the microorganisms, for example peat, compost or stickers. Regardless of methods, the number of cells reaching the soil from commercial products is similar to the existing numbers of soil or rhizosphere microorganisms (Sujatha et al., 2004). These added cells are unlikely to have a beneficial impact on the plant unless multiplication occurs. In addition, the population of introduced microorganisms will decline and be eliminated in a very short time, often days or weeks. The formulation of inocula, method of application and storage of the products are all critical to the success of a biological product. Short shelf life, lack of suitable carrier materials, susceptibility to high temperature, problems in transportation and storage are biofertilizer bottlenecks that still need to be solved in order to obtain effective inoculation. (Abdul Halim., 2009). On the basis of the above principal, the following inoculation methods have been developed:

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Seed Inoculation Seed inoculation uses a specific strain of microbe that can grow in association with plant roots. Soil conditions have to be favorable for the inoculants to perform well. Selected strains of N-fixing Rhizobium bacteria have proven to be effective as seed inoculants for legumes (Gyaneshwar et al., 2002).Seed treatment can be done with any of two or more bacteria without antagonistic effect. In the case of seed treatment with Rhizobium, Azotobacter, Azospirillum along with PSB, first the seeds must be coated with Rhizobium or Azotobacter or Azospirillum. When each seed has a layer of the aforementioned bacteria then the PSB inoculants has to be treated on the outer layer of the seeds. This method will provide maximum numbers of population of each bacterium to generate better results (Antoun et al., 2001). Soil Inoculation In soil inoculation, microbes are added directly to the soil where they have to compete with microbes already living in the soil that are already adapted to local conditions and greatly outnumber the inocula. Inoculants of mixed cultures of beneficial microorganisms have considerable potential for controlling the soil microbiological equilibrium and providing a more favorable environment for plant growth and protection. (Ratti et al., 2001). CROP RESPONSES TO BIOFERTILIZER INOCULATION Tambekar et al., (2009) studied the promoting of plant growth by inoculation with aggregated and single cell suspensions of A. brasilense. They reported that inoculation of single cell suspensions of Azospirillum (prepared with fructose) significantly increased the root surface area, root and foliage dry weight of the maize seedling as compared to plants inoculated with malate grown Azospirillum or the controls. Crops inoculated with Azotobacter and Azospirilla reviewed by Wani (1990) indicated that Pearl millet and Sorghum, which are grown as dry land crops showed 11-12% increased yields due to inoculations. Beans with R. leguminosarum and P. putida increased the number of nodules and acetylene reduction activity (ARA) significantly (de Freitas et al., 1993). Also the findings of Shina et al., (2014) shows that many strains of bacteria native to the soil of (university of Ilorin) have the ability to solubilize phosphorus. However, the degree of solubilization varies from strain to strain. The use of these bacteria as seed inoculants may result in significant improved seed germination, seedling growth and generally increased productivity. A significant positive effect on grain yield and ARA in roots of barley was obtained due to combined inoculation of nitrogen fixer’s A. lipoferum, Arthrobacter mysorens and the phosphate solubilizing strain Agrobacterium radiobacter by Belimov et al. (1995). Radhakrishnan (1996) reported that inoculation of Azospirillum and phospho-bacteria resulted in higher root biomass and more bolls in cotton. Findings of Mohammadi (2010) showed that inoculation of biofertilizers (PSB+ Trichoderma fungi) + application of FYM had a great influence on canola growth, height and grain yield in compared to control treatment. Findings of Mohammadi et al. (2011) showed that application of biofertilizers had a significant effects on nutrient uptake of chickpea combined application of Phosphate solubilizing bacteria and Trichoderma harzianum produced the highest leaf P content and grain P content. These findings also showed that chickpea inoculated with biofertilizers have significantly higher grain protein content. FUTURE PERSPECTIVE OF BIO-FERTILIZERS IN NIGERIA. Excess nutrients are accumulated in soils, particularly P as a result of over application of chemical fertilizers by farmers during intensive agricultural practices. Hence, major research focus 4

should be on the production of efficient and sustainable bio-fertilizers for crop plants, wherein inorganic fertilizer application can be reduced significantly to avoid further pollution problems. In view of overcoming this bottleneck, it will be necessary to undertake short-term, medium, and longterm research, in which soil microbiologists, agronomists, plant breeders, plant pathologists, and even nutritionists and economists must work together. The most important and specific research needs should highlight on following points: 1. Selection of effective and competitive multi-functional bio-fertilizers for a variety of crops. 2. Quality control system for the production of inoculants and their application in the field. 3. Study of microbial persistence of biofertilizers in soil under stressful environments conditions. 5. Transferring technological know-how on biofertilizer production to the industrial level for optimum formulation. 6. Establishment of "Bio-fertilizer Act" and strict regulation for quality control in markets and application. CONCLUSION Bio-fertilizers being essential components of organic farming play vital role in maintaining long term soil fertility and sustainability by fixing atmospheric nitrogen, mobilizing fixed macro and micro nutrients or convert insoluble P in the soil into forms available to plants, there by increases their efficiency and availability. Currently in the country, there is a gap of ten million tones of plant nutrients between removal of crops and supply through chemical fertilizers. In context of both the cost and environmental impact of chemical fertilizers, excessive reliance on the chemical fertilizers is not viable strategy in long run because of the cost, both in domestic resources and foreign exchange, involved in setting up of fertilizer plants and sustaining the production. In this context, organic manures (bio-fertilizers) would be the viable option for farmers to increase productivity per unit area; thus creating an employment opportunity for the teeming youth population. The environmental and health benefits cannot be overemphasizes as biofertilizers are known to be non toxic at any dose. Also the use of biofertilizer will help to conserve the soil and animal life (both flora and fauna) since they stabilize and feed soil and providing nutrients for a very long time thereby preventing soil erosion and conserving ground water. REFERENCES Abdul Halim N.B. (2009): Effects of using enhanced biofertilizer containing N-fixer bacteria on patchouli growth. Thesis Faculty of Chemical and Natural Resources Engineering University Malaysia Pahang. p. 145. Antoun, A and Kloepper, J.W (2001): Plant growth promoting Rhizobacteria. Encyclopedia of genetics pp 1477-1480. Belimov A.A., Kojemiakov A.P. and Chuvarliyeva C.V. (1995): Interaction between barley and mixed cultures of nitrogen fixing and phosphate-solubilizing bacteria. Plant Soil. 173: 29-37. Chima Ngumah, Jude Ogbulie, Justina Orji and Ekpewerechi Amadi (2013): Potential of Organic Waste for Biogas and Biofertilizer Production in Nigeria, Environmental Research, Engineering and Management, 2013. No. 1(63), P. 60-66.

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